This invention relates generally to transmissive screens, and more particularly to transmissive screens suitable for use in rear projection systems.
Rear projection screens are generally designed to transmit an image projected onto the rear of the screen into a viewing space. The viewing space of the projection system may be relatively large (e.g., rear projection televisions), or relatively small (e.g., rear projection data monitors). The performance of a rear projection screen can be described in terms of various characteristics of the screen. Typical screen characteristics used to describe a screen""s performance include gain, viewing angle, resolution, contrast, the presence of undesirable artifacts such as color and speckle, and the like. It is generally desirable to have a rear projection screen that has high resolution, high contrast and a large gain. It is also desirable that the screen spread the light over a large viewing space. Unfortunately, as is described more fully below, as one screen characteristic is improved, one or more other screen characteristics often degrade. For example, in order to increase the screen gain using the same overall structure, the viewing angle over which the screen is readily observable is typically decreased. As a result, certain tradeoffs are made in screen characteristics and performance in order to produce a screen that has overall acceptable performance for the particular rear projection display application.
Thus, there remains a need for screens that have improved overall performance while meeting the minimum performance criteria necessary for the rear projection display application in which the screen is used.
Generally, the present invention relates to rear projection screen assemblies, and particularly to rear projection screens using lenticular lens films as light dispersing components. A lenticular lens film may include lenticular lenses having different focal powers, or may include lenticular lenses formed in two dimensional patterns. The invention is intended to improve the brightness uniformity over the entire screen as viewed by a viewer who is located at a specific position. The specific position is typically selected to be the most probable location of the viewer for the particular application.
In one embodiment, the invention is a rear projection screen for use with a light source, and includes a substrate having first and second transmitting regions. A first lenticular lens pattern is on at least a portion of a first surface of the substrate to provide optical focusing power to the substrate. A first region of the lenticular lens pattern includes focusing elements having a first focal distance and a second region of the lenticular lens pattern includes focusing elements having a second focal distance different from the first focal distance.
In another embodiment, the invention is a rear projection screen, including a substrate having a first surface with a lenticular lens pattern on the first surface. Focusing elements of the first lenticular lens pattern are substantially not linear in extent on the first surface, adjacent focusing elements substantially paralleling one another to form a two-dimensional lenticular lens pattern.
In another embodiment of the invention, a screen includes first transparent light transmitting means for transmitting light, and light dispersing means disposed on at least one surface of the light transmitting means, the light dispersing means including a plurality of light focusing means for focusing light passing through the transmitting means. At least one of the light focusing means has a focal length different from a focal length of another light focusing means.